Introduction to Databases - Chapter 1

Introduction to Databases

• Databases are a shared collection of logically related data designed to meet organizational information needs.
• A system catalog (metadata) describes data, enabling program-data independence.
• Logically related data includes entities, attributes, and relationships of organizational information.

Chapter 1 Objectives

• Common database system uses are covered.
• Characteristics of file-based systems are explored.
• Problems with the file-based approach are examined.
• The meaning of "database" is defined.
• The meaning of "Database Management System (DBMS)" is defined.
• The typical functions of a DBMS are explained.
• Major DBMS environment components are detailed.
• Personnel in a DBMS environment are discussed.
• DBMS development history is reviewed.
• Advantages and disadvantages of DBMSs are analyzed.

Examples of Database Applications

• Purchases from supermarkets.
• Credit card purchases.
• Holiday bookings with travel agents.
• Library usage.
• Insurance applications.
• Video rentals.
• Internet access.
• University studies.

File-Based Systems

• A collection of application programs for end-users (e.g., reports).
• Each program defines and manages its own data.

Limitations of File-Based Approach

• Separation and Isolation of Data: Each program manages its own data, leading to potential unawareness of related data held by other programs.
• Data Duplication: Same data appears in multiple programs, wasting space and potentially leading to inconsistencies.
• Data Dependence: File structure is defined within the program code.
• Incompatible File Formats: Programs written in different languages cannot easily access each other's files.
• Fixed Queries/Proliferation of Application Programs: Programs are written for specific tasks, so new requirements often necessitate new programs.

Database Approach

• Data definition was embedded in application programs rather than being stored independently.
• No control over data access and manipulation beyond application programs.
• Result: The database and Database Management System (DBMS).

Database Management System (DBMS)

• A software system that allows defining, creating, maintaining, and controlling access to a database.
• The DBMS interacts with other programs (application programs) by receiving appropriate requests (SQL statements).

Database Approach (Continued)

• Data Definition Language (DDL): Defines data types, structures, and constraints.
• Data Manipulation Language (DML): Provides general inquiry facilities (query language) for data manipulation.
• Metadata is stored in the database.

Database Systems (Continued)

• Database Management System (DBMS) is software that defines, creates, maintains, and controls data access.
• DBMS uses Data Definition Language (DDL), Data Manipulation Language (DML).
• Query Language (QL) – retrieves data from a database.
• Access Control Language (ACL) - determines access levels.
• Database Administration Language (DAL) – administrates databases (logical or physical level).

Database Approach (Final Points)

• Controlled access to a database may include security, integrity, concurrency, recovery, and user-accessible catalogs.

Views

• Allows users to have their own views of the database.
• Essentially a subset of the database.

Views - Benefits

• Reduce complexity.
• Improve security.
• Customize database appearance.
• Present a consistent, unchanging view of the database even if the underlying database structure changes.

Components of DBMS Environment

• Hardware: From PCs to computer networks.
• Software: DBMS, operating system, network software, and application programs.
• Data: Used by the organization, with a description (schema).
• Procedures: Instructions and rules for database design and use.
• People: Involved in DBMS use (e.g., system analysts, database designers, application developers, DBAs, security administrators, naive and sophisticated end-users).

History of Database Systems

• First-generation: Hierarchical and Network databases.
• Second-generation (CSIT115): Relational databases.
• Third-generation (CSCI235): Object-Relational, Object-Oriented databases.
• Now: Cloud-based databases (e.g., covered in CSC1235).

Advantages of DBMSs

• Controls data redundancy.
• Enforces data consistency.
• Provides more info from the same data.
• Shares data.
• Improves data integrity.
• Improves security.
• Enforces standards.
• Provides economies of scale.
• Balances conflicting requirements, improving data accessibility & responsiveness & productivity.
• Improves maintenance through data independence, concurrency, and backup and recovery services.

Disadvantages of DBMSs

• Complex.
• Large Size.
• High cost of DBMS.
• More hardware costs.
• Costly conversion.
• Impacts of failure are greater.
• Performance Issues.

This quiz covers the essential concepts of databases, including their definition and the functions of Database Management Systems (DBMS). It explores the characteristics of file-based systems and the advantages and disadvantages of using a DBMS. Test your understanding of database applications and the components that make up a DBMS environment.